Rare cell isolation is an important example of an application in which particles (the rare cells) are filtered from a medium (blood). In conventional filters used for this purpose, a plurality of pores is arranged in a layer that extends perpendicular to the flow direction of the filtered medium. A disadvantage of such filters is that the retained cells are often damaged due to high pressure gradients. Moreover, a transfer of the cells is needed if they shall be further analyzed, which means additional stress for the cells.